An ink jet printer includes one or more ink jet heads arranged in a main scanning direction. Printing can be performed by moving a recording medium such as paper in a sub scanning direction relative to the ink jet heads.
One type of an ink jet head used in the ink jet printer includes a head having a piezoelectric element for ejecting ink and a driver IC for driving the piezoelectric element. Further, a circuit board on which the driver IC is mounted and a circuit board on which electronic parts are mounted are enclosed in a casing, in order to prevent ink or a foreign substance from being attached to the driver IC or the electronic parts.
When the driver IC is housed in the casing, it would be preferable to radiate heat generated by the driver IC to the outside of the casing.